Continuous infusion (CI) may be the preferable modality for treatment due to a more precise maintenance of desired plasma factor IX levels and the resulting diminished cost of treatment secondary to an overall decrease in factor IX requirements. Mononine(R), Coagulation Factor IX (Human), Monoclonal Antibody Purified, is approved for factor IX replacement therapy in hemophilia B patients by intravenous (IV) bolus. The clinical safety and efficacy of Mononine(R) replacement therapy administered by CI in mild, moderate, and severe hemophilia B patients during surgery or after trauma or severe spontaneous hemorrhage has been evaluated in an international, multicenter, open-label study. In this trial, factor IX recovery and half-life are determined prior to planned elective surgery (but are not required for actively bleeding patients). Patients first receive an IV bolus injection of product to reach a target factor IX:C level of gtoreq0.4 to 1.0 IU/mL. CI therapy is then initiated to maintain preoperative and postoperative factor IX:C at the same level for up to 6 days. The CI dosage is calculated using the clearance determined for the individual patient. Efficacy of therapy is determined by the investigators in comparison to patients without hemostatic disorders undergoing similar procedures and rated on a five-point scale ("excellent"=normal hemostasis, "good"=slight oozing at surgical site, "fair"=mild bleeding, "poor"=moderate bleeding, "none"=severe bleeding). Twenty-eight patients (25 surgery, 2 trauma, 1 severe spontaneous hemorrhage) were enrolled in to the study. A median intravenous bolus dose of 54.2 IU/kg FIX was administered to a subset of 13 non-emergency patients 7-21 days prior to CIV infusion to determine pharmacokinetic parameters. The overall mean half-life was 16.7 hours (range, 8.7-36.6); mean clearance was 4.5 mL/h/kg (range, 2.5-9.7); and the mean in vivo recovery (IVR) was 1.20 (IU/dL)/(IU/kg) (range, 0.65-1.6). During the bleeding/surgery episode, the median dose of FIX administered by bolus injection was 89.6 IU/kg (range, 12.4-108.3). Following the bolus injection, a median total CIV infusion dose of 396.4 IU/kg (range, 44.9-785.5) was administered at a median rate of 3.84 IU/kg/hour (range, 1.74-7.33) for 107.17 hours (range, 31.75-144). Overall hemostatic efficacy was rated as "excellent" (normal hemostasis) for 23 of 24 (96%) patients and as "good" (slight oozing) for one patient (bilateral knee replacement). Median FIX:C was 72%-86% for all patients receiving FIX by CIV on all days. No patient has experienced thrombotic complications, anaphylaxis, or inhibitor development. Continuous infusion of Mononine(R) resulted in safe and effective hemostatic coverage of surgical procedures and bleeding episodes among patients with mild to severe hemophilia B.